18

CHAPTER II

2.1. REVIEW OF LITERATURE

Plant-parasitic nematodes have been established as serious pathogens on

economic crops. Some of them are known to cause severe economic crop

losses either singly or in association with other micro-organisms in almost

every agro-climatic region. Based on the available information, Meloidogyne

species are major destructive plant pathogens affecting vegetable crops

production and substantially reducing their quality (Roberts, 1987; Trudgill and

Block, 2001; Karssen and Moens, 2006). Among the root-knot nematodes,

Meloidogyne incognita has been cited as major limiting factor on vegetable

crops production in tropical and subtropical countries (Sikora and Fernandez,

2005). Although there are several ways to manage these nematode pests in

developed agricultural systems, protection relies on the use of crop protection,

resistant cultivars and the use of synthetic chemicals. Chemical control is

expensive and not readily available particularly to small farmers in developing

countries including India and these cause a lot of hazards to both animal and

human health and contaminate the environment (Noling and Becker, 1994). As

a result, there is growing interest in methods for nematode management that are

economically viable and not polluting.

The focal theme of the study presented in the current thesis was to

observe the nematicidal/nematostatic properties of various organic soil

amendments, which can be successfully employed for the management of root-

knot nematode, Meloidogyne incognita. As this has already been mentioned in

19

the previous chapter (Introduction) that addition of various organic

amendments like plant parts/products, biocontrol agents and interculture of

antagonistic crop besides some other cultural practices, are the highly

promising and pronouncing strategies for the management and control of

nematodes. Therefore, an attempt has been made in this chapter to summarize

the available literature on these aspects.

The organic matter is an important component of soil and the value of

decomposition of organic amendment is an important factor of soil in reduction

of nematode damage which was first demonstrated by Linford et al. (1938),

who observed the reduction in root-knot incidence caused by Meloidogyne spp.

on cowpea (Vigna unguiculata L.), when soil was amended with chopped

leaves of pineapple (Ananas comosus L.). Since then a large number of reports

have been published showing that the incorporation of a variety of organic

amendments to the nematode infested soil resulted in a definite reduction of

several plant-parasitic nematodes and therefore, improved the crop yield.

Organic amendment of soil has been used since the beginning of the

agriculture. It benefits physical and chemical soil properties, increase soil

fertility and aids in pest control (Garcia Alvarez et al., 2004). Organic soil

amendments used for nematode control are extremely heterogeneous, including

green manures, animal “bed” (sawdust, straw), composts, soil urban residues,

and a variety of agro-industrial by products (Hoitink, 1988; D’ Addabbo, 1995;

Riegel and Noe, 2000; Barbosa et al., 2004; Buena et al., 2007). Among the

large variety of organic material from animal and plant origin that have been

20

tried as biofumigants, agricultural by products, and crop residue, are

increasingly becoming of interest. These phytochemicals are safer to the

environment and humans than traditional chemicals. The soil amending with

different plant parts/products are reported to be effective in reducing root galls

caused by root-knot nematodes and population density affecting a variety of

economic crops and their incorporation in soil also contributes to the nutrient

and organic matter recycling into the system, decreasing the losses in organic

matter and energy, as well as costs needed to compensate those losses (Jesse et

al., 2006; Ahmad et al., 2007b; Buena et al., 2007; Radwan, et al., 2007;

Rather et al., 2007; Rather and Siddiqui, 2007; Ahmad et al., 2008a,b).

Recently, Javed et al., (2008) recorded that soil treatment with neem

crude formulation significantly reduced the intensity of root galling and

number of egg masses caused by Meloidogyne javanica on the roots of tomato.

Mankau (1968) found that the application of alfalfa (Medicago sativa) green

manure in root-knot infested field was found to be a good nematode

suppressant. The application of rapeseed green manure @200, 300 and 400 mg

N/kg soil was more effective than velvet bean green manure in reducing root-

galling caused by Meloidogyne arenaria in squash roots (Crow et al., 1996).

Marigold and sea ambrosia plants have been reported to suppress infection and

damage caused by Meloidogyne incognita, when incorporated as a green

manure (El-Hamawi et al., 2004).

Idowa (1999) observed that mixing of plant-residue, clary sage (Salvia

spp.) used as an organic amendment, was generally less effective in

21

suppressing gall formation and egg production of Meloidogyne incognita on

tomato cv. Rutgers, compared with top soil application. Cassava leaf and tuber

rind applied as soil amendment @100g or 50 g/pot, significantly reduced

population of Meloidogyne incognita and improved plant growth parameters of

okra. The pre-sowing application of amendments was more effective than post

sowing (Ramakrishnan et al., 1999). The degradation of neem (Azadirachta

indica) leaves over a period of six weeks before transplanting the tomato

seedlings significantly reduced the root-knot incidence and improved the shoot

weight and length (Jain and Bhatti, 1988).

A number of indigenous plants have been reported to possess

nematicidal/nematostatic properties and thus, are capable of managing the

populations of various plant-parasitic nematodes. Some of these plants tested

for their antinemic properties by different workers include Leucaena

leucocephale (Paruthi et al., 1987); Azadirachta indica, Pongamia glabra,

Arachis hypogaea (Prasad et al., 1994); Ruta graveolus (Sasanelli and

Addabbo, 1993); Allium sativum, Tagetes spp. (Walia and Gupta, 1997);

Ipomea fistulosa (Alam et al., 1995), Calotropis procera (Rao et al., 1996);

Sargassum spp. (Ara et al., 1997), Linum usitatissimum, Brassica campestris

(Butool et al., 1998) ; Salvia spp. (Idowa, 1999) ; Azadirachta indica A. Juss

(Akhtar, 2000) ; Parkia biglobosa (Umar and Jada, 2000) ; Murraya koengii

(Pandey, 2000) ; Argemone mexicana (Shaukat et al., 2002) ; Catharanthus

rosea, Ipomea fistulosa (Hassen et al., 2003) ; Ilex walkeri, Sarcococca

zeylanica, Diploclisia glaucescens, Hedyotis lawsoniae, Allophylus cobbe,

22

Dimocarpus longan and Lepisanthes teraphylla (Jayasinghe et al., 2003) ;

Calotropis procera, Datura fastuosa, Azadirachta indica (Zarina et al., 2003) ;

Ricinus communis, Brassica juncea, Eruca sativa (Khan et al., 2004); Lantana

camara L. (Qamar et al., 2005) ; Blechum piramidatum, Stenandrium nanum,

Furcraea cahum, Ageratum gaumeri, Ambrosia hispida, Bidens alba, Calea

utricifolia, Acalypha gaumeri, Croton chinensis, Tephrosia cinerea, Trichilia

arborea, T. minutiflora, Randia longiloba, R. obcordata, R. strandleyana

(Cristobal-Alejo et al., 2006) ; Chromolaena odorata L., Azadirachta indica A.

Juss, Ricinus communis L. and Cymbopogon citratus L. (Adegbite and

Adesiyan, 2006) ; Parkia biglobosa, Hyptis spicigera (Jesse et al., 2006) ;

Euphorbia tirucalli, E. neriifolia, Nerium indicum, Thevetia peruviana,

Pedilanthus tithymaloides (Siddiqui, 2006) ; Mucuna pruriens (Zasada et al.,

2006); Tagetes minuta (Adekunle et al., 2007) ; Ficus bengalensis, F. virens

(Ahmad et al., 2007a) ; Azadirachta indica (Javed et al., 2007, 2008) ; Acacia

nilotica, Argemone mexicana, Aristolochia bracteolate, Azadirachta indica,

Calotropis procera, Cassia senna, Chenopodium album, Cucumis melo,

Cymbopogon nervatus, Datura stramonium, Dinbera retroflexa, Eucalyptus

microtheca, Lantana camara, Lawsonia inermis, Nerium oleander, Ocimum

basilicum, Salvadora persica, Solenostemma argel, Trigonella foenum-

graecum and Ziziphus spina-christi (Elbadri, et al., 2008a).

Bello et al. (2006) reported the inhibitory effect of water extract of

seed, leaf and bark of five plants viz., Tamarindus indica, Cassia siamea,

Isoberlinia doka, Delonix regia and Cassia sieberiana against the larval

23

hatching of Meloidogyne incognita. The standard suspensions inhibited larval

hatching by 97% while dilution of S/100 inhibited larval hatch by 3%.

Similarly significant reduction was observed in the population of plant-

parasitic nematodes, Meloidogyne incognita, Rotylenchulus reniformis and

Tylenchorhynchus brassicae infesting eggplant and cauliflower, when the

seedlings were given the root-dip treatment in leaf extracts of Argemone

maxicana and Solanum xanthocarpum (Ajaz and Tiyagi, 2003). The solvent

extracts of the plant species viz., Allophylus cobbe, Lepisanthes tetraphylla,

Sarcococca zeylanica and Hedyotis lawsoniae, were among seven Sri Lankan

plants which showed significant nematicidal activity against Meloidogyne

incognita maintained on tomato (Lycopersicon esculentum) plants (Jayasinghe

et al., 2003).

The oil cakes are generally rich source of manurial ingredients such as

nitrogen, phosphorus and potash (NPK). The effective soil amending with

various oil cakes takes about 1-2 weeks for the decomposition and the

application of such materials leads to a sustained release of nutrients to the

plants, which ultimately results in the suppression of the population of plant-

parasitic nematodes. The oil cakes when amended with moist soils are more

effective than amending with dry soils. The oil cakes of neem/margosa

(Azadirachita indica A. Juss.), castor (Ricinus communis L.), cottonseed

(Gossypium herbaceum L.), groundnut (Arachis hypogea L.), linseed (Linum

usitatissimum L.), mustard (Brassica juncea (L.) Czern and Coss), soybean

(Glycine max Merr.), mahua (Madhuca indica Gmel.), duan/rocket salad

24

(Eruca sativa Mill.), sesame (Sesamum indicum L.), bakain/Persian lilac (Melia

azedarach L.) and karanj (Pongamia pinnata L.), have been extensively used

for the control of a wide range of plant-parasitic nematodes, however, some of

these oil cakes of cotton, groundnut, sesame, linseed, mustard etc., may not be

so economical and feasible when applied as soil amendment for nematode

control and are chiefly used as cattle feed.

Goswami and Meshram (1991) reported a significant decrease in the

root-penetration of Meloidogyne incognita on tomato by the application of

mustard and karanj oil seed cakes and the reduction was almost 50% as

compared to untreated control. Reddy and Khan (1991) observed that the root-

gall index of Meloidogyne incognita infesting okra in fields was significantly

reduced when the soil was amended with various oil cakes viz., castor,

groundnut, karanj and neem, applied singly @1.0 tonne/ha and 0.5 tonne/ha in

combination with carbofuran. Similar results were reported by several other

nematologists while assessing the nematicidal properties of a number of oil

cakes against the population of plant-parasitic nematodes affecting a wide

range of vegetable crops like tomato (Lycopersicon esculentum Mill.), okra

(Abelmoschus esculentus L. Moench), chili (Capsicum annuum L.), eggplant

(Solanum melongena L.) etc. (Alam et al., 1980; Abid and Maqbool, 1991;

Khan et al., 1991; Akhtar and Mahmood, 1997; Rich and Rahi, 1995; Rao et

al., 1997; Butool et al., 1998).

Poornima and Vedivalu (1993) reported that the oil cakes of neem,

castor and mahua alone and in combination with different plant extracts and

25

nematicides were effective in reducing the populations of Meloidogyne

incognita, Pratylenchus delattrei and Rotylenchulus reniformis on brinjal cv.

CO2. Rao et al. (1991) claimed that all oil cakes were effective against the

mushroom nematode, Aphelenchoides sacchari and the yield of Agaricus

bisporous and the treatment of compost with neem, coconut and karanj cakes at

1 to 2% yielded significantly higher crops. Alam (1990) observed that the oil

cakes were effective for the control of plant-parasitic nematodes in nurseries of

many annual crops. The plant growth of Phaseolus mungo was greatly

improved due to the suppression of reproduction and population built up of

Meloidogyne incognita, when the inoculated plants were treated with neem oil

and groundnut cake either alone or in combination (Vaitheeswaran et al.,

2005). Goswami et al. (2006) observed that the maximum reduction in root-

galling caused by Meloidogyne incognita on tomato plants, as well as the

nematode population occurred in soil, treated with both fungi (Trichoderma

viridae and Paecilomyces lilacinus) in combination with mustard cake.

However, mustard cake alone also showed adverse effects on the root-

nodulation.

In 2008, El-Sherif et al., stated that when certain oil cakes viz., fennel,

sesame were used as soil amendments against Meloidogyne incognita on

eggplant, all treatments significantly improved the growth of eggplant and

suppressing the number of galls, females and egg masses of Meloidogyne

incognita as compared to nematode alone. Zahir (2004) reported that sesame

oil cake achieved the highest increment in plant fresh weight (78.92%) with

26

reduction percentage of galls (90.29%) and second stage juveniles/250g soil

(80.39%), whereas harmal oil cakes gave lowest values for root galling

(84.29%) and J2/250g soil (60.13%) compared to nematode alone.

It has been demonstrated by a large number of workers that various oil

cakes when amended in combination with different nematicides are more

effective in reducing the populations of root-knot nematode, Meloidogyne

incognita and various other plant-parasitic nematodes and increased the plant

growth and yield than either of them alone (Anver and Alam, 1996;

Sankaranarayana and Sundarababu, 1997; Goswami et al., 2006; Javed et al.,

2008; Rather, 2008;).

The combined application of various oil cakes and biocontrol agents

have been reported to be an effective approach to minimize the losses caused

by various plant-parasitic nematodes (Rao et al., 1995., Tiyagi et al., 2002;

Borah and Phukan, 2004; Zareena and Kumar, 2005). Ram and Baheti (2004)

pointed out that leaf and seed kernel of neem, castor and karanj, when tested as

seed dresser (10% w/w) along with soil applicant (2.5q/ha) for the management

of Rotylenchulus reniformis on cowpea (Pusa Barsati), were effective in

improving plant growth and reducing nematode population over untreated

check. Similar results were also reported by Dayal and Sharma (2007), who

observed the application of mahua seed kernel @20% w/w to be highly

efficient in enhancing the plant growth characters of mungbean and reducing

the nematode reproduction of Rotylenchulus reniformis, followed by jatropha

seed kernel @20% and mahua seed kernel @10% w/w.

27

Animal manures have been used since the beginning of agricultural food

production to improve soil fertility, recycle nutrients, improve biological and

physical properties of soil and increase crop yield (Rodriguez-Kabana et al.,

1987; Sims and Wolf, 1994). The research with animal manures amended in

soil, have shown that they possess nematode-suppressive properties

(Montasser, 1991; Kalpan and Noe; 1993; Opperman et al., 1993; Stephan,

1995; Oka and Yermiyahu, 2002). The mode of action, however, has not yet

been fully determined. The application of manure enhances soil fertility, aids in

controlling plant-parasitic nematodes and provides a mean of disposing off the

manure.

Ahmad et al., (2008b) reported that incorporation of ficus leaves (Ficus

bengalensis L.) with compost, NPK and nematicides in soil significantly

reduced root-knot development caused by Meloidogyne incognita. These

treatments also helped the tomato plants to attain better height and fresh weight

as compared to untreated inoculated plants. Soil amending with cow dung,

urine and their mixture significantly reduced the extent of root-galling and

nematode multiplication of root-knot nematode, Meloidogyne incognita race 1

and improved the various plant growth parameters of tomato cv. ‘Sokoto’

(Abubakar et al., 2004). Similar results of reduction in nematode populations

by soil amending with cow dung were also reported by Babatola (1990) and

Abubakar and Majeed (2000).

Poultry is an important segment of agricultural production and poultry

litter generated will require improved disposal methods, as environmental

28

regulations become more limiting. Chicken manure is potentially an

environmental contaminant of water and disposal over large land areas is a

desirable option. Chicken litter, a common form of poultry manure, consists of

manure and pine shaving beddings, contains significant quantities of N, P, K,

Ca, Mg and micronutrients and can be used as a substitute for commercial

fertilizers (Ndegwa et al., 1991). Several researchers have reported that the

chicken litter when applied to the soil as an organic amendment will lower the

densities of plant-parasitic nematodes (Gonzales and Canto-Saenz, 1993;

Owino and Waudo, 1995; Riegel et al., 1996; Riegel and Noe, 2000;

Ravichandra et al., 2001; Ribeiro et al., 2002; Ami and Al-Sabie, 2004). This

suppression of nematodes is probably a combination of enhanced microbial

activity and constituent toxicity. The majority of nitrogen in poultry manure is

in the form of uric acid that can be rapidly converted to ammonium nitrogen if

temperature, pH and moisture are suitable for microbial activity (Sims and

Wolf, 1994). The ammonia produced has been shown to kill plant-parasitic

nematodes (Eno et al., 1993). The presence of pine shavings in litter serves as a

carbon source and reduces phytotoxicity caused by the accumulation of

ammonia and nitrates (Huebner et al., 1983).

The biological control of nematodes using rhizosphere microorganisms

was considered in several reviews to be a potential tactic and effective

alternative of nematicides (Sikora, 1992; Kerry, 2000). The contribution to the

biocontrol of plant-parasitic nematodes was reported for a great diversity of

microorganisms including plant growth promoting rhizobacteria (Racke and

29

Sikora, 1992; Siddiqui and Ehteshamul-Haque, 2001; Siddiqui and Shaukat,

2003), bacterial parasites (Singh and Dhawan, 1994), obligate fungal parasites

and facultative fungal parasites (Kok and Papert, 2002), competitors including

both fungal endophytes (Hallmann and Sikora, 1994; Diedhiou et al., 2003) as

well as mycorrhizal fungi (Pinochet et al., 1996; Jaizme-Vega et al., 1997;

Habte et al., 1999; Calvet et al., 2001; Elsen, 2003). Although the biocontrol of

nematodes using rhizosphere microorganisms could be a promising approach to

suppress those pests, the problems associated with these practices under

practical conditions are far from being totally overcome mainly because of too

many species and races occurring naturally. With the current knowledge, it is

difficult to promote or establish a microflora in soils that effectively suppress

nematode population densities especially in the relatively short period of time

of a single growing season (Starr et al., 2002).

In the recent years, continuing environmental problems associated with

the use of nematicides have resulted the search for alternative methods of

nematode management. The control of plant-parasitic nematodes with natural

products of plant and animal origin and soil organisms are alternative control

tactics that are receiving increased interest among nematologists/pathologists.

Natural products include a number of plant parts, byproducts and residues

when incorporated into the soil. One such byproduct of plant origin is

cellulosic waste material. In paper industry large quantity of hemicellulosic

wastes are generated following alkaline and bisulphate treatments of wood to

release the cellulose. The nematicidal effects of soil amendments with paper on

30

meadow nematodes and subsequent Verticillium wilt of tomato was reported

by Miller and Edginton (1962). In a similar treatment, Miller et al. (1968)

found reduced larval emergence as well as root invasion in eggplant by

Heterodera tabacum. Culbreath et al. (1985) observed that the addition of

lingo-hemicellulosic materials to soil amended with chitin could increase the

effectiveness of chitin against the nematodes. Akhtar and Mahmood (1996)

reported that amending the soil, naturally infested with different plant-parasitic

nematodes, with cellulosic wastes and other waste materials such as oil seed

cakes, chitin, compost, live stock and poultry manures, can be effectively

employed against the damage caused by these plant-parasitic nematodes.

Plants appear to be a source of effective pesticidal compounds and may

be regarded as an inexhaustible source of harmless pesticides having low plant

and human toxicity and being easily biodegradable (Prakash and Rao, 1997).

Consequently, a large number of plants/plant parts/plant products have been

screened for their nematicidal activities (Pandey, 1990; Bar-Eyal et al., 2006;

Elbadri et al., 2008a,b; Taba et al., 2008). Although most researchers have

investigated the non-volatile constituents of the plants for their nematotoxic

potential (Sangwan et al., 1990; Ghosh and Sukul, 1992), but little attention has

been given to volatile constituents of essential oil-bearing plants. The essential

oils (sometimes also called as ethereal oils) are a class of vegetable oils, which

are usually chemically complex mixtures of organic substances. Mostly they

are terpene derivatives, phenyl propanoids, various hydrocarbons and straight

31

chain compounds (seldom longer than 20 atoms). They are distinguished from

fixed oils in their physical and chemical properties (Kochhar, 2006).

The emulsified oils of six different plant species viz., canola,

cotton, flax, olive, sesame and soybean were reported to possess the antinemic

properties against Meloidogyne incognita infecting tomato plants. Emulsified

canola oil proved to be the most effective protectant followed by soybean,

cotton, flax and sesame oil. Thus these prepared plant oils might be used as

potential sources for sustainable eco-friendly botanical nematicides to protect

plants from nematode attack (Aly Radwan et al., 2006).

Essential oils are natural volatile substances found in a variety of plants.

They are composed of isoprenoid compounds, mainly mono- and

sesquiterpenes which are the carriers of smell found in aromatic plants

(Franzios et al., 1997). Particular emphasis has been placed on their

antibacterial, antifungal, antimite, antitermite, insecticidal and nematicidal

activities (Franzios et al., 1997; Chang et al., 2000a,b, 2001a,b; Chang and

Cheng, 2002; Adekunle et al., 2007). Volatile oils of Tagetes minuta have

biological activities against a wide range of pests (Mohamed et al., 2000).

Adekunle et al., (2007) reported that pure compounds (z – β – ocemene and

dihydrotagetone) isolated from Tagetes minuta oil showed strong nematicidal

activity against Meloidogyne incognita, with dihydrotagetone showing a higher

level of toxicity than z – β – ocemene.

Abd-Elgawad and Omer (1995), explored the essential oils of four

medicinal plants for phytonematode control. All the oils inhibited nematode

32

mortality but Mentha spicata was generally more effective in reducing the

number of active nematodes followed by Thymus vulgaris, Majorana bortensis

and Mentha longifolia. The main corresponding compound of each oil

determined by GLC analysis was carvone (58.14%), P-cymene (40.5%),

terpinen-4-OL (41.6%) and carvone (70.36%). Soil stages of the reniform

nematode were more affected by the oil than those of the ring and lance

nematodes. The content of oxygenated compounds in these oils ranged from

45.79% to 96.50% and may be partially responsible for the nematicidal effects.

Pandey et al. (2000) reported the nematicidal activity of eight essential

oils against root-knot nematode, Meloidogyne incognita at four different

concentrations viz., 2000, 1000, 500 and 250 ppm. Maximum nematicidal

activity was recorded in oils of Eucalyptus citriodora, E. hybrida and Ocimum

basilicum. Oka et al. (2000b) reported that twelve of twenty seven essential oils

extracted from spices and aromatic plants immobilized more than 80% of

juveniles of root-knot nematode, Meloidogyne javanica at a concentration of

1000 µl/litre and at the same concentration most of these oils also inhibited

nematode hatching.

The effectiveness of soil amendment with either flowers, leaves, roots or

seeds of Chrysanthemum coronarium, and flowers and several species of

Asteraceae (Chrysanthemum segetum, Calendula maritima, C. officinalis and

C. suffructicosa) at 5g/500cm3 soil were evaluated for suppression of cereal

root-knot nematode, Meloidogyne artiellia and growth of chickpea cv. ‘PV 61’.

Similar results have been reported by various other researchers, which are

33

sufficient to believe that the essential oils derived from the higher plants

possess the nematotoxic properties (Leela et al., 1992; Soler-Serratosa, 1995;

Walker and Melin, 1996; Alvarez-Castellonos et al., 2001; Perez and Lewis,

2006).

Latex bearing plants have also shown great potential in the management

of phytonematodes (Siddiqui et al., 1987; Siddiqui, 2006; Ahmad et al.,

2008b). Incorporation of chopped parts of latex bearing plants can bring a

substantial reduction in the population of plant parasitic nematodes. Haseeb et

al., (1978) used chopped leaves of Indian rubber tree (Ficus elastica), madar

(Calotropis procera), and Opuntia dillenii as soil amendment and found

significant control of Hoplolaimus indicus, Tylenchorhynchus brassicae and

some other tylenchids infesting eggplant. Siddiqui et al., (1987) also reported

good control of Meloidogyne incognita and the reniform nematode,

Rotylenchulus reniformis on tomato and eggplant, and T. brassicae on cabbage

and cauliflower where chopped shoot parts of several latex bearing plants were

used.

Most interesting among the nitrogenous amendments that stimulate

specialized soil microfloras are those containing a specialized chitin or similar

mucopolysaccharides. Most nematode species can be significantly reduced by

tilling in chitinous materials such as crushed shells of crustaceans (Shrimp,

Crab etc). This is effective because several species of fungi that feed on chitin

also attack chitin-containing nematode eggs and nematodes. Increasing the

amount of chitin in the soil will also increase the population of these fungi.

34

ClandosanTM, a nematicide made of crab shells and agricultural grade urea can

be effectively used as a pre-plant treatment (Fiola and Lalancettle, 2000). The

soil amending with chitin results in very sharp increase in chitinase activities

which in turn stimulates the activity of chitin decomposing microflora

(Rodriguez-Kabana et al., 1983; Sultana et al., 2000).

Benhamon et al. (1994) reported that chitosan, the deacetylated

derivative of chitin, induces systemic plant resistance against Fusarium

oxysporum f. sp. radicislycopersici in tomato when applied as seed treatment or

soil amendment through induction of physiological and structural changes in

the host plant. Hallmann et al. (1999) demonstrated that the addition of chitin

to soil at 1% w/w eliminated plant-parasitic nematodes in a first planting of

cotton cv. ‘Rowden’ and significantly reduced Meloidogyne incognita

infestation in a second planting. The soil amending with chitin was effective

for control of various plant-parasitic nematodes like Meloidogyne incognita in

tomato (Spiegel et al., 1986; Jayakumar et al., 2004), Heterodera and

Tylenchulus semipenetrans in wheat (Spiegel et al., 1989), Tylenchulus

semipenetrans in orange (Mankau and Das, 1974), Pratylenchus penetrans and

Tylenchorhynchus dubius on cucumber (Miller et al., 1973), Meloidogyne

arenaria (Mian et al., 1982; Godoy et al., 1983), Meloidogyne javanica in

chickpea (Ehtesamul-Haque et al., 1997).

Kalaiarasan et al. (2006) reported that the soil application of chitin

(applied @1% w/w) and chitinolytic biocontrol agents (Pseudomonas

flourescens and Trichoderma viridae @2.5 kg/ha each) promoted the plant

35

growth of groundnut cv. ‘Co3’, to the tune of 39.7% and also increased the

yield of the crop up to 27.8% compared to control. These chitinolytic

biocontrol agents (Pseudomonas flourescens and Trichoderma viridae) also

possess the enzyme activity of lipase, protease, chitinase, glucanase etc.

(Morton et al., 2004). So the possible way of destructing the nematode eggs is

through the action of these lipases and proteases.

The efficient management of plant-parasitic nematodes requires the

carefully integrated combination of several methods. Although each individual

method of management has a limited use, together, they help in reducing the

nematode populations in agricultural soil or in plants more efficiently. With the

on going progress in research, a public desire for methods of

managing/reducing plant pests in ways that are cheap, easily available, eco-

friendly and do not pollute or otherwise degrade the environment, has increased

concomitantly. The integrated pest management (IPM) provides a working

methodology for pest management in sustainable agricultural systems. One

such method employed for maintaining the populations of plant-parasitic

nematodes below the economic threshold level, is the mixed cropping practice,

sometimes also referred to as intercropping, which is a form of multiple-

cropping system using host and non-host crops at the same place and time

(Blair, 1992; Rodriguez-Kabana and Canuilla, 1992). It has been reported by

several workers that different cropping sequences reduce the populations of

some harmful phytonematodes to the levels that do not cause economic losses

36

(Alam et al., 1981; Idowa and Fawole, 1989; Upadhyay et al., 1997; Haider et

al., 2001b).

Haider et al. (2004) reported that the intercropping two rows of yellow

sarson (Brassica campestris var. Toria / Brassica campestris var. sarson) with

sugarcane, recorded the highest reduction (23.7%) in nematode populations

followed by sugarcane + one row of yellow mustard at the time of harvest of

intercrops. This sequence showed prolonged effect of toxicity as evidenced by

21% reduction in nematode population from initial density level at the time of

harvest of sugarcane. Sugarcane + yellow mustard intercropping system

exhibited the highest cane equivalent yield. Similar results of inclusion of

mustard, a poor host for several nematodes, in different cropping sequences for

reducing nematode populations have been reported by several other workers

(Singh and Sitaramaiah, 1993; Kumar et al., 2006). Prasad et al. (2004) found

the highest linseed equivalent when linseed was intercropped with mustard

followed by gram. The decrease in nematode populations by intercropping

mustard could be attributed to the presence of 2-propenyl isothiocynate in

mustard having nematicidal activity as reported by Kowalska and Sonalinska

(2001).

Sundararaja (2005) reported that the maximum reduction in root-lesion

index and nematode population of root-lesion nematode, Pratylenchus coffeae

was observed where marigold (Tagetes erecta) was grown as an intercrop and

was at par with chemical treatment. The yield of banana increased significantly

to 12.5 and 12 kg/plant in plants treated with chemical pesticides and

37

intercropped with marigold respectively, compared to minimum bunch weight

of 7kg/plant in untreated control, but the use of marigold as an intercrop in

banana fields warrants more economical and eco-friendly approach compared

to chemical nematicides. Similar findings were also reported by several

workers who reported that intercropping marigold with different crops can

reduce the population of plant-parasitic nematodes thereby exhibiting a better

plant growth (Dhanger et al., 2002; Moussa et al., 1997; Yen et al., 1998; Uma

Shankar et al., 2005).

Vetrivelkalai and Subramanian (2006) observed that the population

dynamics of several plant-parasitic nematode species increased and maintained

during cropping period but reduced sharply during fallow period in all the

cropping sequences viz., sorghum-fallow, tomato-fallow, cotton-fallow and

blackgram-fallow. The least population of Meloidogyne incognita was

observed during cropping period but not recovered during fallow period in

tomato-fallow and cotton-fallow cropping sequences. Similar results were also

reported by Wani (2005) who observed that the cropping-sequence wheat-chili-

fallow caused greatest reduction in the nematode population followed in the

descending order of efficiency by lentil-cowpea-mung, chickpea-okra-chili,

mustard-mung-tomato and tomato-fallow-okra, however, the extent of field

ploughing also playing an important role, and deep ploughing being more

effective than normal ploughing. Similarly, Cabanillis et al. (1999) reported

that sorghum-fallow and cotton-fallow reduced Rotylenchulus reniformis

populations.

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The crop rotation may provide a short-term suppression of nematode

population densities (Starr et al., 2002). However, due to the polyphagous

nature of the pest as well as the relatively low economic value of some

recommended rotational crops, control of root-knot nematodes by crop rotation

becomes very limited (Waceke et al., 2001). The crop rotation to a non-host

crop is often adequate by itself to prevent nematode population from reaching

economically damaging levels. However, it is necessary to positively identify

the species of plant-parasitic nematodes in order to select appropriate crops,

which should be poor hosts or non-hosts for the prevailing nematode species.

Besides the naturally occurring nematode suppressiveness which has been

reported by several agricultural systems (Kluepfel et al., 1993),

suppressiveness can also be induced by crop rotation with antagonistic plants

such as velvet bean, Mucuna deeringiana (Vargas et al., 1994) and

switchgrass, Panicum virgalum (Kokalis-Burelle et al., 1995).

Natural products with nematicidal potential have been identified by

testing the effect of plant extracts (from leaves, stems, fruits and seeds), oil

extracts, plant exudates and plant volatiles on nematodes that infect plants

(Qamar et al., 2005; Adekunle et al., 2007; Ahmad et al., 2007a; Elbadri et al.,

2008a,b). Application of chopped plant parts to soil were shown to be

nematicidal to root-knot nematodes and to reduce infection of plants (Siddiqui,

2006; Ahmad et al., 2007b; Rather et al., 2007; Ahmad et al., 2008a,b).

Many naturally occurring compounds are known to possess nematicidal

activity (Chitwood, 2002). Plythienyls in Tagetes spp. (Kyo et al., 1990),

39

isothiocynates and glucosinolates from Brassicaceae (Brown and Morra, 1997),

polyacetylenes from Asteraceae (Kogiso et al., 1976), alkaloids (Matsuda et

al., 1989), phenolics (Evans et al., 1984) and pentacyclic triterpenoids from

Lantana camara (Qamar et al., 2005) have been reported to possess

nematicidal activity. Therefore, natural products seem to provide a viable

solution to the environmental problems caused by synthetic pesticides and may

be more readily available and less costly in developing countries including

India for eco-friendly nematode management option.